Improved bridge



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JOHN A LEXANDER'MCKAY, or AUBURN, INDIANA.

Letters Patent No. 90,7 67 dated .Tune l, 1869.

IMPROVED BRIDGE.

Hrs-

The Schedule referred to in these LettrsPatent and making part of the carne.A

To all whom it may concern Be it known that I, Joux ALEXANDER MCKAY, of .Auburn, in the county of De Kalb, and State of Indiana, have invented a new and useful Improvement in Bridges; and I do hereby declare thaty the following is a full, clear, and exact description of the construction and operation of the same, reference being had to the accompanying drawings, making a part of this specification, in .which- Figure 1 is a perspective View, showing one side of the bridge detached. v

Figure 2, a detached horizontal section, showing the lock hereinafter described.

This invention consists- First, in the arrangement of the main and counter'- braces, as hereinafter described, for the purpose of eecting an equilibrium of tension and compression throughout the entire truss; and, l

Secondly, in the arrangement and construction of a metallic shoe, with a suitable wedge, a bolt, and peculiarly-formed ends of the lateral braces, as will be more fully explained.

To enable others skilled in the art to make and use `my invention, I ,will proceed to describe its construction and operation.

A AFA2 represent a series of braces, which extend diagonally through the lower' and upper chords B B', as seen in the drawings, fig..l, at any desired angle from a perpendicular. p

These Abraces are arranged in sets, commencing at the centre of the truss, each set diverging in opposite directions, as seen in iig. 1. l

The braces are single, and extend above and below the upper and lower' chords, and are secured in position by means of suitable bolts, or other equivalent means. Y Y C C C'l represent a series of braces, which correspond to braces A A in every respect, except that these are double, while those are single.

Thes 'c'es are also extended through the chords,

"y are in like marmer bolted, and stand in a. reversed, but correspondingly-diagonal n position to the single ones.

' D represents aV triangular key, which is inserted in Vth I rurgular space formed by the surface of the chord anditli'e surfaces of the braces, both above and-below the said chords, as will be readily understood from the drawings.

Now, it will be observed that the single braces A2 A2 intersect exactly at the centre of the truss, just below the'under surface of the lower chord, where they are keyed, as above described.

They extend thence upward obliquely to a point where they meet, on either side, a set of double braces, whichare marked Cl C, and are at that point keyed and' bolted, as' before, while at the same time each double brace thereafter, in every successive instance,

. both above and below, and throughout the entire truss,

cavity so formed that it will fit the heel of the brace, as shown at m.

N represents a wedge, which is inserted between the ends of the lateral braces, and is held in position by a boit, O, extendingthrough it.

The bolt-is provided with a tightening-nut, e.

The whole device forms a streng but simple lock, which prevents the braces from being withdrawn, and admirably fits them for thel successful resistance of.

tension orzcempression, thus effectually preventing all lateral motidn. g

The operation of the above-described combination of braces forming my truss, is as follows:

When a weight is placed at any given point of said truss, as, for instance, at the centre, the result will be to create a tension on braces G2 O2, and also to create a corresponding compression on braces A2 A, the effect of which is to create a compression of that section of the upper chord, between the braces OZAZ, and also a compression of that section of the chord between the intersection of the braces Cl A.

But suppose that the weight is shifted to a point marked x, the effect would be to reverse the order of the tension and compression, so that the braces that before sustained the tension now sustain the compression, and m'ce versa.

rlhus the compression and tension, in practice, will be ever changing at every successive point to which' the weight is removed, thereby perfectly equalizing the strain over the entire length of the truss.

By' this arrangement for controllingthe tension and compression of the braces, the top chord is not in the least liable to kink or buckle.`

Another important advantage of this system of bracing is, that it prevents the bridge from swelling in front of the load, as in many other bridges.

What I claim as new, and desire to secure by Letters Patent, is-

lhe combination of the chords B B', the single and double braces A Al A2, each bolted to the chords in dependently of all the others, and the triangular blocks I), intervening between the adjacent ends ofthe braces, when said parts are constructed and arranged substantially in the manner and for the purpose herein set forth.

J. A. MCKAY.

Witnesses z H. F. WILLsoN, J. S. Gosnoln. 

